Absorption of 3H-benzocaine from ointments following rectal administration in rats

Total radioactivity in the blood of rats for 5 hr following rectal administration of 3H-benzocaine in oleaginous, absorption, emulsion (water-in-oil and oil-in water), and water-soluble ointment vehicles was measured. The release was greatest from the water-soluble vehicle and followed the same relative order as seen in an earlier in vitro experiment. No intact benzocaine was found in the blood using radiochromatography. In vitro hydrolysis of benzocaine by rat blood did not occur as determined with the techniques of this experiment.